van der Waals Equation



  • The parameter b is related to the size of each molecule. The volume that the molecules have to move around in is not just the volume of the container V, but is reduced to ( V - b )
  • The parameter a is related to intermolecular attractive force between the molecules, and 1/V is the density of molecules. The net effect of the intermolecular attractive force is to reduce the pressure for a given volume and temperature.
  • When the density of the gas is low (i.e., when 1/V is small and b is small compared to V)  the van der Waals equation reduces to that of the ideal gas law.